Lajos,
FÖLDY Lajos wrote:
>
> On Fri, 4 Apr 2008, Allan Whiteford wrote:
>
>>
>> Brian,
>>
>> Even if they had, it would probably[1] be in violation of the GPL to
>> distribute such code.
>>
>
> There is an FFTW3 DLM on the ITTVIS website. FFTW3 is GPL and ITTVIS
> distributes this DLM (binary only). So, is ITTVIS violating GPL?
>
Once again, IANAL. I note that you can buy a non-GPL version of FFTW3,
maybe ITTVIS did this in which case discussions are academic.
The whole argument comes down to the difference between linking code and
aggregating code and exactly how two pieces of code communicate. It has
been discussed ad-nauseum by thousands of people and I'm not really in a
position to give a more informed opinion than anyone else. Debian legal
discussions are a good place to look for technical discussions rather
than just flamewars.
The FSF and GPL seem to draw the line somewhere between a SO/DLM/DLL
approach and using a fork and exec. My understanding is that if you have
a GPL library then you couldn't distribute a program which links against
it (either statically or dynamically) without that program becoming GPL.
See this:
http://www.gnu.org/licenses/gpl-faq.html#IfLibraryIsGPL
which seems fairly definitive and this:
http://www.gnu.org/licenses/gpl-faq.html#GPLPluginsInNF
which is coming from the opposite point of view but would still suggest
that a non-free main program can't have a GPL plug-in without special
permission from the plug-in author. I think plug-in could be considered
to mean something called via linkimage, call_external in the context of
IDL.
> Actually, IDL is not linked against the DLM, IDL is a standalone
> executable. The user links in (loads) the DLM at run-time using the
> DLM hook provided by IDL. Is this the same as build-time linking?
>
I think the FSF and GPL don't see a difference (see last link above).
It might be worth looking into the organisation of the Linux HAL - but
that's a GPL main program with proprietary plug-ins rather than the
other way around.
> I am working on the DLM sup****t for FL and my example program is FFTW3.
> I plan to release the DLM source under GPL. Is this enough? What is your
> opinion?
Some people would certainly assert that that would make all of FL GPL
but that's not to say they'd be right (although I think within open
source software circles they will be in the majority).
My personal opinion and understanding of the GPL would be that this
would be a violation but I'm not an expert on these things by any
stretch of the imagination.
I would be very cautious about releasing a FFTW3 plug-in for FL.
You can always write to the FSF for advice and/or contact the FFTW3
people to see if they'll make an exception for FL.
Thanks,
Allan
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